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The utility said the work will start July 25, but it's already setting up traffic control in some areas.

The big underground transmission line runs from northwest to northeast Bakersfield, and the project is what company officials call "hydrostatic testing."

PG&E started tests like this in 2011. One of these tests near Bakersfield was the first that failed.

Back in late October that year, the utility was testing a line in a field near Nord and Brimhall. The line blew out, ripping a long hole in the big pipe. The utility said later it was probably a weld that failed.

The current test project will affect an area of Clay Patrick Farr Way between Meachem and Winlock. PG&E said southbound traffic on Clay Patrick Farr Way will be reduced to one lane for a short stretch.

The test will also impact the intersection of Coffee Road and Downing Avenue. During the first construction phase, westbound traffic will be cut from four lanes to two. Then, during a second phase, the southbound right-turn lane and bike lane, a crosswalk and sidewalk will be closed during the test. Drivers will see flaggers in the area.

Then, starting about July 17, other areas will be affected. PG&E said the eastbound Highway 178 Union Avenue exit will be closed during parts of the construction. Also at Fruitvale Avenue and Downing a shoulder will be closed.

Finally, at Gibson Street north of Gilmore Avenue, expect northbound Gibson to be closed with flaggers directing traffic. Then, southbound lanes at Gibson and Gilmore will close, with flaggers directing traffic in three directions. Also, drivers will see flaggers at Gilmore and Standard Street.

With hydrostatic tests, gas is first "vented" from the pipeline. PG&E said that may result in a temporary odor of gas, but that does not pose a risk to the public.

During these tests, the pipeline is taken out of service for several days, but customers will get gas from another source. During the test a section of the pipe is sealed off.

"This test involves pressurizing a section of pipe with water to a much higher level than the pipe will ever operate at with natural gas," according to a fact sheet from PG&E. "The test will validate a safe operating pressure for the pipeline and can also reveal weaknesses that could lead to defects and leaks."

If the section of pipe doesn't meet required standards during the test, it's replaced with new pipe that has passed a pressure test. That's what crews did with the area of pipe near Nord and Brimhall in 2011.

For this summer's local test, PG&E also will have an open house to answer questions from the public. A spokesman said information about that meeting will be released in a week or two. The pipe test is projected to wrap up by the end of August.